Engine/Transmission (1998.5 - 2002) Poor mileage & performance

[BLudington]

I've got a stock 2001 SLT, LB, 4WD with auto trans, 104K, owned since new and recently my everyday mileage dropped from 19 mpg to 16. 5 mpg. Then last weekend I was pulling a new 18ft enclosed V nose toy hauler (weight 3500 lbs) and my mileage was only 10. 5 mpg over 700 miles (no wind). This was the first time I'd pulled the enclosed trailer and could not believe how poor the mileage and performance were when I'd pulled open flatbeds with 7000 lbs and got 14. 5 to 16 mpg. The trans was downshifting much more than normal and at times dropping all the way down to 2nd gear on a slight incline. Filters are all new and trans oil and filter changed within the last 5K (not burnt or dirty and very minimal metal filings in pan and on mag). I don't hear the turbo spooling up any more (could be my hearing) but in my everyday driving I don't notice any real performance issues other than mileage. Would I know if the turbo was out if I wasn't putting my foot in it or pulling a load? Looking for ideas.



Bruce

 

[AKAMAC]

Welcome to the site!

Check for boost leaks. Do you have gauges?

Mike

 

[BLudington]

No gauges. But that does bring up the next question. Is there a point in vehicle mileage where it isn't realilistic to be dumping money into performance modifications? A point where I could actually be decreasing the integrity of the engine.



Bruce

 

[mmclaughlin]

The gauges wouldn't really be considered performance mods - just a good way to keep track of what's going on. Sounds like a boost gauge should be in order, and if you don't have one yet, a fuel pressue gauge. There has been a lot of talk on the boards about the MAP sensor going bad causing poor perfomance, along with a boost leak that was mentioned before. You mentioned that you had all new filters - so I'm guessing that means the air filter. If you have your truck loaded up with a trailer, you should hear the turbo spool up - if not, that may be your problem. Take a look at the blades on the turbo to see if there is any visable damage, spin it to make sure it's spinning freely. If everything is ok there, make sure you check all the hoses to make sure there is no leak anywhere.



- m

 

[Slim's Ram]

check your intercooler hoses, my intercooler hose blew of of my truck causing poor performance, fuel mileage, and my boost pressure went from 20 to 25 too 0 to 10. hope this helps in your search for the problem.

 

[Texas Diesel]

Winter blend fuel? I always see a decrease with winter fuel.

 

[CSnyder]

i have also been experiencing the same symptoms but with a manual transmission. I recently changed out my APPS and that helped some. then I cleaned my IAT sensor and that also helped but it still seems like my mileage has dropped even running the same fuel blend of #2

 

[AKAMAC]

One spot to check for a leak is where the soft rubber line touches the A/C line below the oil filter. It can rub through on the pressure switch.

Mike

 

[Hohn]

I've got a stock 2001 SLT, LB, 4WD with auto trans, 104K, owned since new and recently my everyday mileage dropped from 19 mpg to 16. 5 mpg. Then last weekend I was pulling a new 18ft enclosed V nose toy hauler (weight 3500 lbs) and my mileage was only 10. 5 mpg over 700 miles (no wind). This was the first time I'd pulled the enclosed trailer and could not believe how poor the mileage and performance were when I'd pulled open flatbeds with 7000 lbs and got 14. 5 to 16 mpg. The trans was downshifting much more than normal and at times dropping all the way down to 2nd gear on a slight incline. Filters are all new and trans oil and filter changed within the last 5K (not burnt or dirty and very minimal metal filings in pan and on mag). I don't hear the turbo spooling up any more (could be my hearing) but in my everyday driving I don't notice any real performance issues other than mileage. Would I know if the turbo was out if I wasn't putting my foot in it or pulling a load? Looking for ideas.



Bruce

Bruce, you WOULD notice if the turbo went out, even just tooling around town. The CTD is built with the turbo as an integral part, not just an add on. It will smoke like crazy if the turbo is bad. The computer is also programmed to limit fueling if there's no boost, so you will notice a LOT less power as well.



You can assume your turbo is OK. It may be wearing and becoming less efficient, but it should be fine still.



Enclosed trailers often cause a big drop in mileage simply because they have much more wind resistance. With this kind of load, the speed you drive has a HUGE effect on mpg.



I'm not sure anything is out of line here. .



jlh

 

[WestTN]

If you haven't pulled an enclosed trailer before,then you have just been introduced to aerodynamics. The weight of a trailer isn't nearly as significant as the aero drag on fuel mileage. My truck gets better mileage with my full height camper on than it does when the bed is empty and I am pulling my little 6 x 10 enclosed trailer.

 

[Wiredawg]

Enclosed Trailers get less MPG

I don't get much better pulling my 10K lb 20' enclosed car hauler than I do my 17K lb 5th wheel. Big difference in aerodynamics.



Wiredawg

 

[BLudington]

Appreciate all the replies. Sounds like a set of gauges is in order if I'm do do any type of trouble shooting on my own.



Bruce

 

[JR2]

Have you checked your truck for codes?? You can cycle the key on and off three times (leaving the key on the third time) and watch for codes in the odometer window. If you have a bad MAP sensor your truck could be in limp mode?? My Dad drove his truck in limp mode for a couple of weeks and complained of a shortage of power.



I would also check your boost hoses, when I tightend up my Dad's the first time he was blown away with the performance increase he saw. He had a boost gauge and was only seeing 17psi instead of 21 or so max. It makes a huge difference.